E333 - Calcium citrates:
Citric acid was the first additive that was produced on a large scale biotechnically. The classic method used the metabolic power of certain fungi (Aspergillus niger).
Research has been undertaken with genetically modified Aspergillus niger to obtain higher yields. It is possible that these methods are already used commercially.
Irrespective of possible gene modifications, citric acid-producing microorganisms grow on culture media that usually contain molasses (sugar beet)) and/or glucose. Glucose can be produced form maize starch. This can be derived from GM maize.